Ben 10 Crystal Gems
by amberisafossil
Summary: Cross over with new Gems and old enemies. With lots of twists and turns.
1. Introduction

Over 6,000 years ago an alien race known as Gems tried to colonize the planet Earth. However their actions were unsuccessful as a group of Gems known as the Crystal Gems fought against their Homeworld to protect Earth. After a thousand years of war the Crystal Gems won, and Homeworld Gems left Earth alone. However it was won at a great cost. A once large are of Gems was reduced to just 4 Gems left on Earth; Garnet, Amethyst, Pearl, and their leader: Rose Quartz. While Gem activity was secede on Earth, there where still dozens of dangerous Gem artifacts left on Earth and the Crystal Gems protected Earth from them. They also protected Earth from other alien species that threatened the Earth. In modern times a group of humans and aliens know as the Plumbers protected the Earth from extraterrestrial threats. While they knew about the Gem race they didn't know about the failed colonization, the war, or the Gem artifacts left on Earth. They never knew about any Gem activity on Earth, including the Crystal Gems. In fact the Crystal Gems stayed as far away from the Plumbers as possible and have remained undetected, until now.


	2. Ben meet the Gems

In Bellwood there was a large explosion and Ben, Gwen, and Kevin raced to it. When they got there they saw large green centipede like creatures with a single eye in the middle of their mouths.

"Time to take them out with Humongasour!" Ben the turned into Humongasour. He squashed some of the Centipeedles, and they just poofed into nothing under his feet.

"That's _unusual_." Gwen pointed out. She then summoned mana and blasted it at some other Centipeedles and the same result as with Ben; poofed into nothingness.

The other Centipeedles then grew mad and some shot a green liquid at Ben and Gwen. They dodged it, but when it hit the wall behind them it melted the concrete wall into a pile of goop.

" _Acid_ spit?! Seriously?!" Kevin complained. A Centipeedle appeared behind him and shot acid at him. He dodged it, but barely.

Gwen put a mana shield around her and Kevin. But the Centipeedles just melted it with their acid spit.

" _How_ can we beat these things?" Ben said, who was still in Humongasour mode.

Then a purple whip came out of nowhere and tossed a cluster of Centipeedles into a wall, causing them to poof. A girl holding the other end of the whip appeared. She looked to be 14 with light purple skin, long silver hair that covered her left eye, magenta pupils, wore a dark purple shoulder strap shirt with the right strap hanging over her arm, black pants with a star cut hole at the knees, white boots, and had a hexagonal amethyst gem on the top of her chest, which was partly covered by her shirt. She walked over to the area where she poofed the Centipeedles with her whip.

"Hey you guys, these things _don't_ _have_ gems." The girl said, who apparently was calling out to someone.

Then a taller girl appeared next to the purple one. This one looked to be 21, had dark reddish brown skin, a black square Afro, silver sunglasses on her face that covered her eyes, wore a light red jumpsuit with puffy sleeves, a white star with a pink outline on the lower right side of the top, the leg part of the suit was pure black that had black heels on the bottom, had black arm gloves that revealed her palms, which had a square garnet gem in the left palm, and a triangle garnet gem in the right palm.

"Then that can only mean _one_ thing." She said. A Centipeedle jumped behind her, but she lifted her arm back and hit it with her knuckles.

"There _must_ be a Mother somewhere." A voice said. It came from a girl who walked behind the first two. She looked to be at 17, had pale white skin, had blonde hair in a ponytail on the back of her head, had blue eyes, wore a light blue sleeveless shirt with a small yellow star in the top middle, a light pink see through skirt with blue short shorts, green boots, and had a white oval pearl on the higher part of her forehead.

Three Centipeedles jumped behind her, but her gem glowed and she pulled a white spear from it and sliced them. "If we find and destroy the Mother, all these little, _creatures_ , will vanish." Her spear then vanished into pure light.

The Centipeedles then ran away. The three girls then started to walk away. "Before we leave we should get Steven his Cookie Cats." The purple one said. Then they all walked away.

"Who, or _what_ are they?" Kevin asked, who was in shock.

"Don't know, but I'm _going_ to find out." Ben said, and was back in human form.

"They mentioned Cookie Cats, so they must have gone to get some." Gwen said.

"And there is only one store with those. I'll turn into Nanomech and follow them to where ever they go." Ben then turned into his alien and flew off.

He followed them to the store and saw them walking out with Cookie Cats. "I really don't get what's in these things that makes Steven love these." The white one said.

Ben followed them into the woods where they walked on a crystal pad with small steps on it. He landed on to of the pad which glowed and then a stream of light appeared around the pad and teleported them to another pad, but this one was in a house.

Then the purple on put the Cookie Cats in the freezer, the her and the other two went into the door behind the warp pad and the door shut closed.

Ben turned back into human form and walked out of the house. He saw the ocean and walked towards the town on the other side of the hill the house was built under. He noticed a giant stone woman with eight arms above the house. The town's name was Beach City. It was a small town about ten miles from Bellwood. Ben pulled out his communicator and called Gwen and Kevin and told them his location.

"Hello. What's your name?" A voice said.

Ben turned around and saw a small boy, maybe 10 or 11, with curly brown hair, light skin, full black irises, wore a salmon pink T-shirt with a s large gold star in the middle, blue jeans, and salmon pink sandals.

"Uh, Ben. Ben Tennyson. What's your name?" Ben asked.

"Steven. Steven Universe. What brings you to Beach City?"

"I'm waiting for some friends."

"Want some fry bits?"

A horde of Centipeedles then came out of nowhere and attacked Ben and Steven.

"Run!" Steven said.

"I got this. SWAMPFIRE!" Ben said and then transformed into his alien.

He then burned the Centipeedles to a crisp.

"So _cool_!" Steven said.

Then the three girls from before appeared in front of them.

"A methanosian?! _How_ did one get on Earth?!" The white one said.

"Don't care! _Destroy_ it!" The purple one then summoned a whip from her gemstone and wrapped it around Swampfire and pulled him into the air.

Then the red one jumped and smacked him on to the ground with her gauntlets that she summoned from her gemstones. She then came crashing down in a comet of fire at Swampfire.

"NO! DON'T HURT HIM!" Steven then jumped in front of him and then summoned a shield from a pink glow from under his shirt. The red girl bounced off of it.

"He summoned his _weapon_?!" The white one said.

"He was protecting that hep of... _whatever_ that is?" The purple one sounded confused.

Ben then turned back into human form.

"It's a _human_? But it was just a _methanosian_ a second ago. Wait, does that mean he's the one with the Omnitrix?" The red one speculated.

"Garnet, Amethyst, Pearl, why did you try to kill my new friend?" Steven asked.

"Sorry Steven, we thought he was a _true_ methanosian, not just the skin of one."

"You. Red one. Why do you know about the Omnitrix?" Ben asked.

Just then Gwen, and Kevin pulled up in Kevin's car. "Hey, it's those girls from before! Just _what_ are they?" Kevin said.

"Let's take them back to the Plumbers. Grandpa might know what they are." Gwen said.

"Guess we couldn't hide from them _forever_." The white one said.

"Guess it's time we make ourselves known to them. They _do_ have a right to know." The red one said.

"I'm coming too!" Steven said as he trailed behind them.


	3. Old reunion

The Gems, Steven, Ben, Gwen, and Kevin all pulled up at Max's store. They went to the secret entrance and went into Plumber HQ.

"Ben, I got your message. What is it?" Max said.

"That voice. It can't be. Max?" The white one said as she turned around to face Max.

Max was in shock.

"No way. Pearl? How can this be? You haven't aged a day since I last saw you like, what, 42 years ago?"

"41 years, three hundred fifty two days, seven hours, and 13 minutes." Pearl corrected him.

"And I thought Gwen had a good memory." Ben whispered to Kevin.

"You two know each other? How?" Gwen asked Max.

"We dated a long time ago. But I wasn't aware that she was a Gem until just now." Max said.

"How do you know about Gems? And what is this place?" Steven asked.

"This place is the Plumbers. We protect the Earth from inhuman catastrophes." Max answered.

"Gems? Is that what you are?" Kevin asked the girls.

"Yes. I'm Pearl." Pearl said.

"I'm Amethyst." Amethyst said.

"And I'm Garnet." Garnet said.

"Why do you guys have stones on your bodies?" Ben asked as he pointed to their gems.

"These 'stones' are the literal cores of our beings that we can't exist without." Garnet said sounding offended.

"So wait, you dated her, Pearl, but didn't find it strange that she had a giant pearl on her forehead?" Gwen asked Max, changing the subject.

"She must have hid it under her hair so I couldn't see it." Max speculated.

"Yes. I didn't want you to know what I really was." Pearl said.

"How did you even get to Earth without the Plumbers ever knowing in the first place?" Max changed the subject.

"We've been here for over 5,000 years. Long before the Plumbers ever existed." Amethyst said.

"Wait, you have been around for over 5,000 years?!" Ben sounded shocked.

"Way way longer then that." Pearl said.

"So wait, are you like immortal or something?" Gwen questioned.

"Gems technically can't die from aging or any diseases, but we can be killed." Garnet said.

"Wow. You guys must have like great-times-a-thousand-grandparents alive today!" Ben said.

Amethyst giggled. "We don't have parents. Since we can't die from aging, unlike you humans, our kind doesn't need to have babies with one another, unlike species that do die have to."

Pearl looked annoyed. "What Amethyst is trying to say is that since Gems don't die naturally we don't need to, much less can't, reproduce with our own kind. It was actually thought to be impossible for a Gem to reproduce at all."

"What do mean by "thought to be impossible"?" Kevin asked.

"While it's absolutely impossible for Gems to produce offspring with our own kind, it isn't impossible for a Gem to have an offspring with another species." Garnet said.

"I'm one of those!" Steven said as he jumped.

"He's half human half Gem?" Gwen asked.

Steven then pulled up his shirt, revealing a pink gem with a pentagonal facet. "See?"

"Unfortunately his mother, Rose Quartz, had to gave up her physical form to give birth to him." Pearl said sadly.

"Wow. That must have taken a lot of heart for her to do that." Ben said.

Just then there was a loud rumble. Then live feed from the street showing a large Centipeedle rampaging through the streets.

"What is that?!" Max yelled.

"Those things attacked earlier." Gwen said.

"It's the Mother!" Garnet said.

"Let's go smash it!" Amethyst yelled.

"We must be careful!" Pearl added.

"'Mother?'" Max asked.

Pearl turned to Max. "It is the creator of the Centipeedles. So it would be the Mother Centipeedle."

"Who cares what it's called?! How do we destroy it?!" Kevin yelled.

"You can't." Amethyst said.

"It's exoskeleton is as hard as steel and it's acid is able to eat through anything." Pearl said.

"This is a Gem problem. It needs to be solved by Gems. We can't allow any casualties or accidents to happen because we were careless about bring along others." Garnet said bleakly.

"But this is our town and our planet. We need to protect it from that!" Ben said.

"Ha! You couldn't even handle the little ones! What makes you think you can deal with the large one?" Amethyst said.

"It's true. Before they showed up we were almost melted by their acid." Gwen said.

"Well, if you insist, you can come watch. It would be a good idea to have a little back up incase things go wrong." Pearl said.

"Like we need help!" Amethyst said.

"We're coming either way." Kevin said.

"But Steven stays here." Pearl said.

"Why?!" Steven complained.

"Your powers are still a bit... Oh what's the right words?…"

"Uncontrollable,unpredictable, dangerous?" Amethyst said.

Pearl had an annoyed look on her face. "In short, until you have better control over your gem leave protecting humanity to use."

"Poo." Steven said under his breath.

Ben, Gwen, Kevin, and the Gems left to go deal with the problem.

"Oh and Max could you please keep an eye on Steven and make sure he doesn't leave the building until we get back? As a favor to an old friend?" Pearl asked as she saw Steven trying to follow them.

"Sure. I'll make sure nothing happens to him." Max said as he picked up Steven, who crossed his arms.

On the monitor they both watched the battle, which was full of acid.

"Excuse me, but where is the bathroom?" Steven asked.

"Down the hall then left."

Steven then left. But Max then saw Steven take a right, the way out.

"Oh man! The old pretending-to-go-the-bathroom-but-are-really-leaving trick! I can't believe I fell for it!" Max said as he ran after Steven.

When he went outside he saw the Mother Centipeedle trying break free from Amethyst's whip.

Garnet then used her gauntlets to crush the Centipeedle and it disappeared into a poof of clouds and a small spherical green gem fell from where it's eye was. Garnet then approached the gem and a bubble formed around it.

"Why did you put it in a…bubble?" Gwen asked.

"If we don't it will regenerate and will cause trouble again." Garnet said.

"But wouldn't it just pop when it regenerates?" Kevin asked.

"The bubble keeps it from regenerating. So it can't regenerate unless the bubble pops." Pearl said.

"But that is why we'll take it to keep it safe." Amethyst said.

"That was so cool!" Steven said.

"Steven?!" The Gems said.

In a green building on a remote planet

"You want me to do what again?" A voice.

"I want you to check on the Earth projects." Another voice said.

"But what if there are Gems on the planet? We can't operate if the are Gems on the planet!" The first voice said.

"Fine. If it makes you feel better we'll send a Red Eye to check for Gem presence."

 **I'm** **also doing things that aren't based off episodes of either series. And I'm open to suggestions as well.**


End file.
